Astaxanthin inhibits nitric oxide production and inflammatory gene expression by suppressing I(kappa)B kinase-dependent NF-kappaB activation.

Abstract

Astaxanthin, a carotenoid without vitamin A activity, has shown anti-oxidant and anti-inflammatory activities; however, its molecular action and mechanism have not been elucidated. We examined in vitro and in vivo regulatory function of astaxanthin on production of nitric oxide (NO) and prostaglandin E2 (PGE2) as well as expression of inducible NO synthase (iNOS), cyclooxygenase-2, tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta). Astaxanthin inhibited the expression or formation production of these proinflammatory mediators and cytokines in both lipopolysaccharide (LPS)-stimulated RAW264.7 cells and primary macrophages. Astaxanthin also suppressed the serum levels of NO, PGE2, TNF-alpha, and IL-1beta in LPS-administrated mice, and inhibited NF-kappaB activation as well as iNOS promoter activity in RAW264.7 cells stimulated with LPS. This compound directly inhibited the intracellular accumulation of reactive oxygen species in LPS-stimulated RAW264.7 cells as well as H2O2-induced NF-kappaB activation and iNOS expression. Moreover, astaxanthin blocked nuclear translocation of NF-kappaB p65 subunit and I(kappa)B(alpha) degradation, which correlated with its inhibitory effect on I(kappa)B kinase (IKK) activity. These results suggest that astaxanthin, probably due to its antioxidant activity, inhibits the production of inflammatory mediators by blocking NF-kappaB activation and as a consequent suppression of IKK activity and I(kappa)B-alpha degradation.

Full text

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Mol. Cells, Vol. 16, No. 1, pp. 97-105
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Astaxanthin Inhibits Nitric Oxide Production and Inflammatory
Gene Expression by Suppressing Iκ κB Kinase-dependent
NF-κ κB Activation

Seon-Jin Lee, Se-Kyung Bai, Kwang-Soon Lee, Seung Namkoong, Hee-Jun Na, Kwon-Soo Ha, Jeong-A Han,
Sung-Vin Yim1, Kwang Chang, Young-Guen Kwon, Sung Ki Lee2, and Young-Myeong Kim*
Vascular System Research Center and Department of Molecular and Cellular Biochemistry, Kangwon National University Biology,
Chunchon 200-701, Korea;
1 Department of Pharmacology, School of Medicine, Kangwon National University Biology, Chunchon 200-701, Korea;
2 Department of Food Science in Animal resources, College of Animal Resource Science, Kangwon National University Biology,
Chunchon 200-701, Korea.

(Received June 4, 2003; Accepted June 18, 2003)

Astaxanthin, a carotenoid without vitamin A activity,
has shown anti-oxidant and anti-inflammatory activi-
ties; however, its molecular action and mechanism
have not been elucidated. We examined in vitro and in
vivo regulatory function of astaxanthin on production
of nitric oxide (NO) and prostaglandin E2 (PGE2) as
well as expression of inducible NO synthase (iNOS),
cyclooxygenase-2, tumor necrosis factor-α α (TNF-α α),
and interleukin-1β β (IL-1β β). Astaxanthin inhibited the
expression or formation production of these pro-
inflammatory mediators and cytokines in both lipopoly-
saccharide (LPS)-stimulated RAW264.7 cells and pri-
mary macrophages. Astaxanthin also suppressed the
serum levels of NO, PGE2, TNF-α α, and IL-1β β in LPS-
administrated mice, and inhibited NF-κ κB activation as
well as iNOS promoter activity in RAW264.7 cells
stimulated with LPS. This compound directly inhib-
ited the intracellular accumulation of reactive oxygen
species in LPS-stimulated RAW264.7 cells as well as
H2O2-induced NF-κ κB activation and iNOS expression.
Moreover, astaxanthin blocked nuclear translocation
of NF-κ κB p65 subunit and Iκ κBα α degradation, which
correlated with its inhibitory effect on Iκ κB kinase
(IKK) activity. These results suggest that astaxanthin,
probably due to its antioxidant activity, inhibits the
production of inflammatory mediators by blocking
NF-κ κB activation and as a consequent suppression of
IKK activity and Iκ κB-α α degradation.


* To whom correspondence should be addressed.
Tel: 82-33-250-8831; Fax: 82-33-244-3286
E-mail: ymkim@kangwon.ac.kr
Keywords: Cytokine; Inflammation; NF-κB; Nitric Ox-
ide; Reactive Oxygen Species.


Introduction

Inflammation is characterized by the release of pro-
inflammatory cytokines such as tumor necrosis factor-α
(TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6),
as well as inflammatory mediators, including nitric oxide
(NO) and prostaglandin E2 (PGE2), that are synthesized
by inducible nitric oxide synthase (iNOS) and cyclooxy-
genase (COX). These inflammatory mediators and cyto-
kines are involved in the causation of many human dis-
eases including rheumatoid arthritis, asthma, atheroscle-
rosis, and endotoxin-induced multiple organ injury
(Guslandi, 1998; Ritchlin et al., 2003; Simons et al.,
1996). Anti-inflammatory agents reduce the inflammatory
response by suppressing the production of inflammatory
cytokines and mediators (Leach et al., 1998; Makarov,
2000).
Nuclear factor-κB (NF-κB) has a seminal role in immu-
nity, because it activates pro-inflammatory genes encoding

Abbreviations: COX-2, cyclooxygenase-2; DCFH2-DA, 2′, 7′-
dichlorofluorescein diacetate; DMEM, Dulbecco’s modified
Eagle’s medium; IFNγ, interferon-gamma; IKK, IκB kinase; IL-
1β, interleukin-1beta; iNOS, inducible nitric oxide synthase;
LPS, lipopolysaccharide; NF-κB, nuclear factor-kappa B; NO,
nitric oxide; NOx, nitrite plus nitrate; PAGE, polyacrylamide
gel electrophoresis; PBS, phosphate-buffered saline; PGE2,
prostaglandin E2; RT-PCR, reverse transcriptase-polymerase
chain reaction; TNF-α, tumor necrosis factor-alpha.
Molecules
and
Cells
KSMCB 2003

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98 Regulation of NF-κB-dependent Inflammatory Gene Expression by Astaxanthin
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iNOS, COX-2, TNF-α, IL-1β, and IL-6 (de Vera et al.,
1996; Makarov, 2000). It is activated by phosphorylation,
ubiquitination, and subsequent proteolytic degradation of
the IκB protein by activated IκB kinase (IKK) (de Martin
et al., 1993). The liberated NF-κB translocates to the nu-
cleus and binds as a transcription factor to κB motifs in the
promoters of target genes, leading to their transcription.
Aberrant NF-κB activity is associated with various in-
flammatory diseases, and most anti-inflammatory drugs
suppress inflammatory cytokine expression by inhibiting
the NF-κB pathway (Castrillo et al., 2001; Keifer et al.,
2001). Thus, an NF-κB inhibitor has clinical potential in
inflammatory diseases.
Antioxidants such as α-tocopheryl succinate (Neuzil et
al., 2001) and probucol (Dichtl et al., 1999) inhibit NF-
κB activity and block the expression of pro-inflammatory
genes as well as production of NO and PGE2 (Pahan et al.,
1998). Astaxanthin is a non-pro-vitamin A carotenoid,
abundant in vegetables and fruits; it is also present in ma-
rine animals. Astaxanthin and astaxanthin-like products
are commonly indicated as antioxidants (Kurashige et al.,
1990) and immune modulators (Bennedsen et al., 1999).
One effect of astaxanthin is to scavenge reactive oxygen
species (ROS) (Mortensen et al., 1997). However, the
mechanism of its anti-inflammatory action has not been
elucidated.
We hypothesized that astaxanthin regulated the produc-
tion of NO, PGE2, and pro-inflammatory cytokines by
inhibiting NF-κB activation. We showed in RAW264.7
cells stimulated with LPS that it inhibited in vitro and in
vivo production of NO and PGE2 as well as production of
pro-inflammatory cytokines, such as TNF-α and IL-1β.
Furthermore, it suppressed NF-κB activation and iNOS
promoter activity by inhibiting IKK activity. These results
support the idea that astaxanthin prevents inflammatory
processes by blocking the expression of pro-inflammatory
genes as a consequence of suppressing NF-κB activation.


Materials and Methods

Materials Dulbecco’s modified Eagle’s medium (DMEM), peni-
cillin, and streptomycin were from Life Technology Inc. (Rock-
ville, MD). LPS (Escherichia coli O111:B4) and astaxanthin were
obtained from Sigma (USA). Poly (dI-dC) and NF-κB-specific
oligonucleotide were from Promega (Madison, WI), and mono-
clonal iNOS antibody was from Transduction Laboratories (Lex-
ington, KY). Polyclonal antibodies for IκB kinase (IKK), COX-2,
TNF-α and IL-1β were obtained from Santa Cruz Biotechnology
(Santa Cruz, USA). 2′, 7′-dichlorofluorescin diacetate (DCFH2-
DA) was purchased from Molecular Probes (Eugene, OR). Other
chemicals were from Sigma (USA) unless otherwise indicated.

Macrophage isolation and cell culture Cells of the murine
macrophage cell line RAW264.7 were cultured in DMEM (2
mM L-glutamine, 100 units/ml penicillin, 100 mg/ml strepto-
mycin) containing 10% fetal bovine serum (HyClone Labs,
Logan, UT). Peritoneal macrophages were collected from the
peritoneal cavity of 6- to 8-week-old female BALB/c mice
(Daihan-Biolink, Korea) and given an intraperitoneal (i.p.) in-
jection of 1.5 ml of thioglycollate broth (4%) 7 days before har-
vest. Cells were cultured in 12-well plates (3 × 106 cells/well) or
6-well culture dishes (5 × 106 cells/well) at 37°C in 5% CO2/
95% air for 8 h. They were treated with LPS (10 µg/ml) in the
presence or absence of various concentrations of astaxanthin.

Animal treatment Mice (6 to 8 week-old female BALB/c mice,
Daihan-Biolink, Korea) were injected i.p. with LPS (4 mg/kg)
and/or astaxanthin (40 mg/kg). After 12 h, blood was withdrawn
by cardiac puncture. Serum was prepared by centrifugation at
12,000 × g for 20 min at 4°C and kept at −20°C until use.

Measurement of nitric oxide metabolites, cytokines, and
PGE2 Nitrite, a stable oxidized product of NO, was measured in
culture media using the Griess reagents (Kim et al., 1997). Se-
rum nitrite plus nitrate (NOx) concentration was determined
with a nitrate reductase-based colorimetric assay kit (Alexis San
Diego, USA). PGE2 concentrations were determined by enzyme
immunoassay (Amersham Pharmacia Biotech, Piscataway, NJ)
and levels of TNF-α and IL-1β in culture media and sera were
determined by ELISA (R&D Systems, Minneapolis, MN).

Western blot analysis Cells were incubated with or without
LPS in the presence or absence of astaxanthin. They were har-
vested, washed twice with ice-cold phosphate-buffered saline
(PBS), resuspended in PBS containing 0.1 mM phenylmethyl-
sulfonyl fluoride (PMSF), and lysed by three cycles of freezing
and thawing (Koo et al., 2002). Cytosolic fractions were ob-
tained as supernatants after centrifugation at 12,000 × g at 4°C
for 20 min. Protein content was determined by the BCA method
(Pierce, Rockford, IL), and samples (30 µg of protein) were
separated on 8% SDS-PAGE and transferred to nitrocellulose
membranes. The membranes were blocked with 5% nonfat milk
in PBS containing 0.1% Tween 20 (PBST) for 2 h, and incu-
bated with monoclonal mouse-iNOS or polyclonal COX-2 anti-
bodies in PBST containing 1% nonfat milk for 2 h. After wash-
ing three times with PBST, the membranes were hybridized with
horseradish peroxidase-conjugated secondary antibodies for 1 h.
Following five washes with PBST, they were incubated with
chemiluminescent solution for 2 min, and protein bands visual-
ized on X-ray film.

Reverse transcription-polymerase chain reaction (RT-PCR)
Total RNA was obtained from RAW264.7 using the Trizol re-
agent kit (Life Technology Inc., USA). Three µg of mRNA was
converted to cDNA by treatment with 200 units of reverse tran-
scriptase and 500 ng of oligo-dT primer in 50 mM Tris-HCl (pH
8.3), 75 mM KCl, 3 mM MgCl2, 10 mM DTT, and 1 mM dNTPs
at 42°C for 1 h. The reaction was stopped by heating at 70°C for
15 min and three µl of the cDNA mixture was used for enzy-

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Seon-Jin Lee et al. 99
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matic amplification. PCR was performed in 50 mM KCl, 10 mM
Tris-HCl (pH 8.3), 1.5 mM MgCl2, 0.2 mM dNTPs, 2.5 units of
Taq DNA polymerase, and 0.1 µM each of primers for iNOS,
COX-2, TNF-α, and IL-1β. Amplification conditions were:
denaturation at 94°C for 5 min for the first cycle and for 45 s
starting from the second cycle, annealing of iNOS at 47°C for
45 s, annealing of COX-2, TNF-α, and IL-1β at 51°C for 45 s,
and extension at 72°C for 30 s for 35 cycles. Final extension
was performed at 72°C for 10 min. The PCR products were
electrophoresed on a 1.5% agarose gel and stained with
ethidium bromide. The primers used were 5′-TTTGGAGCAG-
AAGTGCAAAGTCTC-3′ (sense) and 5′-GATCAGGAGGGA-
TTTCAAAGACCT-3′ (antisense) for iNOS, 5′-CCGTGGTG-
AATGTATGAGCA-3′ (sense) and 5′-CCTCGCTTCTGATCTG-
TCTT-3′ (antisense) for the COX-2, 5′-ATGAGCACAGAAAG-
CATG-3′ (sense) and 5′-TCACAGAGCAATGACTCC-3′ (an-
tisense) for TNF-α, 5′-ATGGCAACTGTTCCTGAAC-3′ (sense)
and 5′-TTAGGAAGACACGGATTC-3′ (antisense) for IL-1β,
and 5′-TCCTTCGTTGCCGGTCCACA-3 (sense) and 5′-CGT-
CTCCGGAGTCCATCACA-3′ (antisense) for β-actin.

Electrophoretic mobility shift assay RAW264.7 macrophages
were treated with LPS in the presence or absence of astaxanthin
for 2 h and nuclear extracts prepared as described previously
(Kim et al., 1997). A double stranded NF-κB-specific oligonu-
cleotide (5′-AGTTGAGGGGACTTTCCCAGGC-3′) was la-
beled with [γ-32P] ATP by T4 polynucleotide kinase and purified
on a G-50 Sephadex column. The nuclear extracts (10 µg of
protein) were incubated with ∼40,000 cpm (∼0.5 ng) of 32P-
labeled oligonucleotide for 20 min at room temperature as de-
scribed (Kim et al., 1997), and samples separated on a 5% na-
tive polyacrylamide gel that was dried and subjected to autora-
diography.

Assay of iNOS promoter activity Transient transfection and
assay of iNOS promoter activity were carried out as described
(Kim et al., 2001). In brief, a murine iNOS promoter-luciferase
construct was transfected into RAW264.7 cells by the liposome
method. The cells were cultured overnight in DMEM supple-
mented with 10% fetal bovine serum and treated with LPS in the
presence or absence of astaxanthin for 12 h. Cells were lysed
with Reporter lysis buffer (Promega) or buffer containing 1%
Triton X-100, 5 mM dithiothreitol, 50% glycerol, 10 mM EDTA,
and 125 mM Tris-phosphate (pH 7.8). Luciferase activity was
measured by luminometer.

Immunoprecipitation and kinase assays Cells treated with
LPS or astaxanthin were harvested and washed with PBS, and
the pellets resuspended in 80 µl of immunoprecipitation lysis
buffer (50 mM Tris-HCl, pH 7.6, 150 mM NaCl, 10% glycerol,
1% Nonidet P-40, 5 mM EDTA, 1 mM DTT, 100 mM NaF,
2 mM sodium pyrophosphate, 2 mM sodium orthovanadate,
1 mM PMSF, 10 µg aprotinin, and 10 µg leupeptin per milliliter)
and stored on ice for 20 min before centrifugation (14,000 × g,
20 min, 4°C). The IKK complex was immunoprecipitated by
incubation for 1 h at 4°C with polyclonal IKKα antibody bound
to protein-A Sepharose. The immunoprecipitates were washed
twice with immunoprecipitation buffer and twice with kinase
buffer (20 mM HEPES, pH 7.4, 20 mM β-glycerophosphate,
20 mM MgCl2, 2 mM DTT, 0.1 mM sodium orthovanadate).
Kinase assays were initiated by the addition of 2 µM GST-IκBα
fusion protein as substrate, and 0.5 µCi [γ-32P]ATP. Reactions
were incubated for 30 min at 30°C and stopped by the addition
of 2× SDS-PAGE sample buffer. Phosphorylation of the IκBα
proteins was measured by SDS-PAGE followed by autoradio-
graphy and densitometry.

Measurement of intracellular ROS RAW264.7 cells cultured
in a 60 mm-dish at 5 × 105 cells/dish were treated with LPS for
20 min. DCFH2-DA (5 µM) was added to the cultures and incu-
bated for 30 min. The cells were harvested and washed three
times with PBS, and intracellular ROS was quantified by flow
cytometry with excitation at 488 nm and emission at 525 nm.

Statistical analysis Data are presented as the means ± SD of at
least three separate experiments. Comparisons between groups
were analyzed by Student’s t-test. P values of 0.05 or less were
considered statistically significant.


Results

Astaxathin inhibits the production of NO and PGE2 by
suppressing iNOS and COX-2 expression NO and PGE2
are produced by immune activated macrophages, and at
inflammatory sites (Guastadisegni et al., 2002; Mino et
al., 1998). We determined if astaxanthin influences the
production of NO and PGE2 by RAW264.7 cells exposed
to LPS. The cells accumulated nitrite, as a stable oxidized
product of NO, in the culture medium when stimulated
with LPS, and astaxanthin inhibited NO production with
an IC50 of ~5 µM (Fig. 1A); it did not affect cell viability
as measured by the crystal violet staining method (data
not shown). To see whether astaxanthin inhibited NO
production by suppressing iNOS gene expression, we
examined its effect on levels of iNOS protein. Western
blot analysis showed that stimulation of iNOS protein
levels by LPS was completely inhibited by 50 µM astax-
anthin (Fig. 1B). It also inhibited induction of iNOS
mRNA (Fig. 1C), and blocked the increase in PGE2 with
an IC50 of ~30 µM (Fig. 1D). In addition, western blot
and RT-PCR analyses showed that astaxanthin inhibited
expression of COX-2 protein and mRNA, and blocked
COX-2 expression at a concentration of 50 µM (Figs. 1E
and 1F). These results show that astaxanthin inhibits NO
and PGE2 production by suppressing, respectively, iNOS
and COX-2 expression in LPS-stimulated RAW264.7
macrophages.

Astaxanthin suppresses production of TNF-α α and IL-

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100 Regulation of NF-κB-dependent Inflammatory Gene Expression by Astaxanthin
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A B



C





D E




F




Fig. 1. Astaxanthin (AX) inhibits production NO and PGE2 as
well as expression of iNOS and COX-2. RAW264.7 cells were
stimulated with LPS (10 µg/ml) in the presence or absence of
different concentrations of astaxanthin. Nitrite (A) and PGE2
levels (D) were measured after 16 h. Data shown are means ±
SD (n ≥ 3). (B) After 16 h, cells were harvested and levels of
iNOS (B) and COX-2 (E) were measured by Western blotting.
The blot was rehybridized with actin antibody to verify equal
loading of protein. Levels of iNOS (C) and COX-2 mRNAs (F)
were determined in LPS-stimulated cells after 8 h by RT-PCR.
Actin was used as an internal control. Further details in Materi-
als and Methods.


1β β To examine the effects of astaxanthin on inflammatory
cytokine production, levels of TNF-α and IL-1β were
measured in culture media by ELISA. Stimulation of
RAW264.7 cells with LPS dramatically increased secreted
TNF-α and IL-1β levels, and these increases were sub-
stantially inhibited by astaxanthin (50 µM) (Figs. 2A and
2D). TNF-α and IL-1β are expressed as inactive pro-
forms, cleaved into the active forms by TNF-α-converting
enzyme and interleukin-1β-converting enzyme, and se-
creted (Black et al., 1997; Thornberry et al., 1992). West-
ern blot analyses showed that astaxanthin treatment re-
duced intracellular levels of these pro-forms (Figs. 2B and
2E), and also reduced levels of their mRNAs (Figs. 2C
and 2F). Thus astaxanthin inhibits expression of TNF-α
and IL-1β, probably at the transcriptional level.

Astaxanthin suppresses NO, TNF-α α, and IL-1β β pro-
duction by peritoneal macrophages We also examined
the effect of astaxanthin on NO, TNF-α, and IL-1β pro-
duction by primary cultured peritoneal macrophages iso-
lated from female BALB/c mice and cultured in 12-well
A D







B E




C F




Fig. 2. Astaxanthin inhibits TNF-α and IL-1β expression in
LPS-stimulated RAW264.7 cells. RAW264.7 cells were cultured
with LPS (10 µg/ml) in the presence or absence of astaxanthin
for 12 h. and TNF-α (A) and IL-1β levels (D) were determined
in the culture media by ELISA. ** p < 0.01. Intracellular levels
of TNF-α (B) and IL-1β (E) were measured by Western blot
analyses and levels of TNF-α (C) and IL-1β mRNAs (F) were
determined in LPS-stimulated cells after 8 h by RT-PCR. Fur-
ther details in Materials and Methods.


plates for 8 h. NO production increased upon LPS-
stimulation, and this increase was suppressed by 50 µM
axtaxanthin (Fig. 3A) as was the increase in iNOS (Fig.
3B) and in TNF-α and IL-1β levels (Figs. 3C and 3D).

Astaxanthin inhibits NO, PGE2, TNF-α α, and IL-1β β
production in vivo NO, PGE2, TNF-α, and IL-1β are
critical mediators of the inflammatory process and of or-
gan injury in endotoxemia and sepsis (Cunha et al., 1994;
Simons et al., 1996). To examine the anti-inflammatory
effects of astaxanthin in septic animals, we tested whether
astaxanthin affects the production of NO, PGE2, TNF-α,
and IL-1β in LPS-treated mice. As expected astaxanthin
inhibited the increases in plasma nitrite plus nitrate (NOx)
and PGE2 (Figs. 4A and 4B) as well as those of TNF-α
and IL-1β (Figs. 4C and 4D). Clearly astaxanthin inhibits
the production of inflammatory mediators under inflam-
matory conditions.

Astaxanthin suppresses NF-κ κB activation and iNOS
promoter activity NF-κB activation plays a critical role
in the expression of the inflammation-associated enzymes,
iNOS and COX-2, as well as of the cytokines, TNF-α and
IL-1β (Kiemer et al., 2003) that are involved in the
chronic inflammation and pathogenesis of human in-
flammatory diseases (Guslandi, 1998). We tested whether

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Seon-Jin Lee et al. 101
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A B








C D








Fig. 3. Effects of astaxanthin on TNF-α and IL-1β production in
mouse peritoneal macrophages. Peritoneal macrophages from
female BALB/c mice (6- to 8-week old) were cultured in 6-well
culture dishes (5 × 106 cells/well) for 8 h and treated with LPS
(10 µg/ml) in the presence or absence of different concentration
of astaxanthin for 24 h. (A) Nitrite levels in the culture medium
and (B) intracellular iNOS levels. TNF-α (C) and IL-1β (D)
were measured in the culture medium by ELISA. * p < 0.05, **
p < 0.01. Further details in Materials and Methods.


astaxanthin regulates NF-κB activation in LPS-stimulated
RAW264.7 cells and found that the increase in NF-κB-
DNA binding activity in nuclear extracts of LPS-
stimulated macrophages was markedly inhibited (Fig. 5A)
suggesting that astaxanthin inhibits the expression of
iNOS, COX-2, TNF-α, and IL-1β by blocking NF-κB
activation. Murine and human iNOS promoters contain
functional NF-κB binding sites (de Vera et al., 1996; Xie
et al., 1994) and NF-κB activation plays a key role in the
transcriptional activation of the iNOS gene (Yokoseki et
al., 2001). We examined whether astaxanthin suppresses
iNOS promoter activity by blocking NF-κB activation.
LPS treatment of RAW264.7 cells resulted in a 3.7-fold
increase in iNOS promoter activity that was suppressed
by the NF-κB inhibitor pyrrolidine dithiocarbamate
(PDTC) as well as by astaxanthin (Fig. 5B).

Astaxanthin inhibits LPS-dependent nuclear translo-
cation of the NF-κ κB p65 subunit, degradation of Iκ κBα α,
and IKK activation Translocation of NF-κB to the nu-
cleus is preceded by the phosphorylation, ubiquitination,
and proteolytic degradation of IκBα (Baeuerle and
Baichwal, 1997). We measured cytosolic and nuclear NF-
κB p65 subunit levels following treatment with LPS in
the presence or absence of astaxanthin by Western blot
analysis. LPS treatment decreased cytosolic p65 subunit
A B








C D








Fig. 4. Astaxanthin decreases plasma levels of NO, PGE2, TNF-
α, and IL-1β production. Mice were injected i.p. with LPS (4
mg/kg) following pretreatment with astaxanthin (40 mg/kg).
After 12 h, whole blood samples were withdrawn by cardiac
puncture. (A) Plasma levels of nitrite plus nitrate (NOx) meas-
ured with a nitrate assay kit, and plasma levels of PGE2 (B),
TNF-α (C), and IL-1β (D) measured by ELISA. Data are means
± SD (n = 6). * p < 0.05. Further details in Materials and
Methods.


and increased nuclear p65 (Fig. 6A) and astaxanthin
treatment inhibited this translocation. Since nuclear trans-
location of NF-κB is directly linked to IκB degradation
(Butcher et al., 2001), we next examined the effect of
astaxanthin on this proteolytic event. Western blot analy-
sis showed that levels of IκBα declined within 30 min of
LPS treatment, and this decrease was blocked by astaxan-
thin (Fig. 6B). Degradation of IκBα is largely dependent
on its phosphorylation by IKK activation (Pan et al.,
2000), and we found that a three-fold increase in IκBα
phosphorylation and IKK activity in response to LPS was
suppressed by astaxanthin (Figs. 6C and 6D).

Astaxanthin suppresses the LPS-induced increase in
ROS and H2O2-induced NF-κ κB activation NF-κB acti-
vation by LPS is inhibited by antioxidants (Ma and Kin-
neer, 2002). We measured intracellular levels of ROS by
FACS analysis following treatment of cells with PBS in
the presence of DCFH2-DA. LPS induced a marked in-
crease in intracellular ROS, and this increase was strongly
inhibited by astaxanthin (Fig. 7A). Astaxanthin pretreat-
ment also suppressed the increase in intracellular ROS in
RAW264.7 cells that were subsequently incubated with
exogenous H2O2 (data not shown). We next examine
whether astaxanthin regulates H2O2-mediated NF-κB ac-
tivation. H2O2 treatment activated NF-κB, and activation